Williams P B, Dolen W K, Koepke J W, Selner J C
Allergy Respiratory Institute of Colorado, Denver.
Ann Allergy. 1992 Jul;69(1):48-52.
Interest in immunoassay standardization has prompted development of specific IgE assays reporting results related to the international IgE reference. To examine the single point calibration curve employed in the modified RAST assay (MRT) to convert MRT counts to IgE units, independent dilutions of a 25 kU/L total IgE reference and nine allergic sera (three each for short ragweed, cat, and timothy) were made in horse serum and assayed. In a log-log plot, the single point curve was, by definition, linear over its entire range; the dilution curve was curvilinear because of reagent system saturation, which was at 7 kU/L. Curves were not parallel (P less than .001). Allergen-specific dilution curves showed saturation points at values similar to or less than the total IgE system. The linear portions of these curves paralleled the total IgE dilution curve but not the single point curve. This lack of parallelism would have resulted in varying magnitudes of error in estimation of IgE antibody levels in the upper and lower assay ranges, and would imply a lower detection limit for IgE than that which the assay actually has. Modified RAST assay is not appropriate in research or a clinical situation in which accurate quantitative results are needed. Modified RAST assay would furthermore be an inappropriate means of assigning units to proposed reference preparations for standardization.
对免疫测定标准化的关注促使了特定IgE测定法的发展，这些测定法报告与国际IgE参考标准相关的结果。为了研究改良RAST测定法（MRT）中用于将MRT计数转换为IgE单位的单点校准曲线，在马血清中对25 kU/L总IgE参考标准品和九份过敏血清（豚草、猫和梯牧草各三份）进行了独立稀释并进行测定。在对数-对数图中，根据定义，单点曲线在其整个范围内是线性的；稀释曲线由于试剂系统饱和而呈曲线状，饱和点在7 kU/L。曲线不平行（P小于0.001）。过敏原特异性稀释曲线的饱和点值与总IgE系统相似或更低。这些曲线的线性部分与总IgE稀释曲线平行，但与单点曲线不平行。这种缺乏平行性会导致在测定范围的上限和下限估计IgE抗体水平时产生不同程度的误差，并且意味着IgE的检测限低于该测定法实际具有的检测限。改良RAST测定法不适用于需要准确定量结果的研究或临床情况。此外，改良RAST测定法也不适用于为标准化提议的参考制剂指定单位的方法。
